WO2002093742A1 - Integrated dvb filter - Google Patents
Integrated dvb filter Download PDFInfo
- Publication number
- WO2002093742A1 WO2002093742A1 PCT/IB2002/001614 IB0201614W WO02093742A1 WO 2002093742 A1 WO2002093742 A1 WO 2002093742A1 IB 0201614 W IB0201614 W IB 0201614W WO 02093742 A1 WO02093742 A1 WO 02093742A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- filter
- chebyshev
- pass filter
- frequency
- pass
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
- H03H11/12—Frequency selective two-port networks using amplifiers with feedback
- H03H11/1291—Current or voltage controlled filters
Definitions
- the invention relates to a filter for processing frequency signals, preferably received, particularly digital television signals.
- a main field of application of such a filter is, for example, its use in digital video broadcast (DVB) systems with mainly radio frequency (RF) and intermediate frequency (IF) stages at the receiver front end such as, for example, a DVB receiver, a set top box or a video card built in a personal computer.
- DVD digital video broadcast
- RF radio frequency
- IF intermediate frequency
- the adjacent picture carrier (standard-dependent frequency) should be attenuated by at least 20 dB.
- A/D converters with a sampling rate of 30 MHz are used in the state of the art.
- frequency components of more than 15 MHz and 20 dB must be attenuated.
- the invention allows full implementation in an integrated circuit while using a comparatively small number of components, so that an external application will be superfluous. Furthermore, the configuration according to the invention does not require any equalization. By switching the frequency by means of the control device provided in accordance with the invention, the bandwidth can be adjusted in dependence upon the selected transmission system standard. Finally, the invention provides an optimum between a proportionally large suppression of the adjacent channel picture carrier, a proportionally large suppression of the aliasing components for an A D conversion, a flat group delay time in the passband and a proportionally small amplitude fluctuation in the passband.
- An integrated filter with a small amplitude and group delay time ripple in the passband, which is switchable in dependence upon the standard, can thus be realized by means of the invention.
- the invention is particularly suitable for use in DVB systems in which the DVB signal should preferably be converted in such a way that the lower band limit for all standards is 1 MHz.
- the Chebyshev filter is preferably a higher-order Chebyshev filter.
- a 4 th -order Chebyshev filter has proved to be very advantageous.
- the Chebyshev filter may comprise a plurality of filter stages.
- the use of two filter stages has proved to be very advantageous, with each filter stage being preferably formed as a 2 nd -order filter stage.
- the Chebyshev filters should suitably have a ripple of less than 0.5 dB so that a very effective suppression of the disturbing frequency components in the DVB signal can be realized.
- the all-pass filter should be implemented as a higher-order all- pass filter, with a 2 nd -order all-pass filter having proved to be very advantageous.
- the all-pass filter should suitably smooth the group delay time ripple produced in the passband to a value of less than 75 ns.
- the control device preferably comprises a frequency synthesizer so that the frequency can be very exactly switched and adjusted in dependence upon the selected standard.
- the frequency synthesizer generates a reference signal at a reference frequency and the control device further comprises a reference low-pass filter which shifts the phase of the reference signal by 90°, and a phase detector which compares the phase positions of the reference signal and the output signal of the reference low -pass filter and generates an output signal for controlling the frequency position of the Chebyshev filter, the all-pass filter and the reference low-pass filter.
- a circuit is particularly also used for eliminating disturbing temperature influences and process spreads in the control signal of the control device.
- a capacitor which is charged or discharged by the differential current at the output of the phase detector may be connected to the output of this phase detector.
- a buffer memory may be connected to the output of the phase detector, through which buffer memory the output signal of the phase detector is passed.
- Fig. 1 is a block diagram of a circuit arrangement comprising a tuner, a surface acoustic wave filter, a down-converter, a DVB filter and a common A/D converter and DVB channel decoder;
- Fig. 2 is a diagram and a table illustrating standard-dependent frequency responses and group delay times as well as picture carrier frequencies; and Fig. 3 is a preferred embodiment of a filter according to the invention.
- Fig. 1 is a block diagram of a part of a DVB receiver in which a DVB filter is used.
- the circuit arrangement shown comprises a tuner 2 which converts a radio frequency (RF) input signal into an intermediate frequency (IF) signal which is smoothed in a subsequent surface acoustic wave filter 4. Subsequently, the IF signal thus smoothed is applied to a down-converter 6 in which a frequency conversion takes place.
- the output signal of the down-converter 6 passes through a DVB filter 8 before it is further processed in a common A/D converter and DVB channel decoder 10.
- Fig. 2 is a diagram illustrating standard-dependent frequency responses and group delay times, as well as a table illustrating standard-dependent picture carrier frequencies with respect to different DVB television standards.
- a digital transmitter is to receive and the strong carriers of an analog adjacent channel are to be suppressed.
- a maximum amplitude ripple of less than 0.6 dB and a maximum group delay time ripple of less than 100 ns is admissible in the passband.
- the adjacent picture carrier (with standard- dependent frequency) should be attenuated by at least 20 dB.
- a D converters with a sampling rate of 30 MHz are generally used.
- Fig. 1 shows an embodiment of the DVB filter 8 of Fig. 1.
- TP1 first 2 nd -order filter
- TP2 second 2 nd -filter
- the group delay time ripple of the Chebyshev filter 11, 12 is smoothed by means of this all-pass filter 13.
- the Chebyshev filter 11, 12 has a ripple of less than 0.5 dB so as to suppress the interfering frequency components in the DVB signal.
- the group delay time ripple produced in the passband is smoothed to less than 75 ns by the all -pass filter 13 (see Fig. 2).
- a frequency synthesizer 14 is provided, which generates a reference signal at a reference frequency fref, which reference signal is applied to a reference low-pass filter 16 and a phase detector (PD) 18.
- the reference low-pass filter 16 shifts the phase of the reference signal nominally by 90°.
- the phase detector 18 compares the two phase positions and generates a differential current at its output, which differential current charges or discharges a capacitor C.
- the voltage Ucontrol thus formed at the capacitor C is passed through a buffer 20 and is used as a control voltage with which the frequency position of the reference low -pass filter 16, the filters 11 and 12 and the all-pass filter 13 is controlled.
- the phase detector 18 changes the control voltage Ucontrol via its current output and thus changes the filter frequencies as long as the phase difference between its input signals is 90°.
- the circuit components 14 to 20 described hereinbefore constitute a control device for controlling the filters 11 and 12, and the all-pass filter 13.
- the standard switching is performed by switching the reference frequency fref of the frequency synthesizer 14.
- the phase detector 18 thereby controls the filters 11 and 12 and the all-pass filter 13 at the desired reference frequency.
- the control described hereinbefore serves for eliminating unwanted temperature influences and process spreads so as to maintain the control voltage Ucontrol at the desired value.
Landscapes
- Superheterodyne Receivers (AREA)
- Noise Elimination (AREA)
- Networks Using Active Elements (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002590502A JP2004534444A (en) | 2001-05-11 | 2002-05-08 | Integrated DVB filter |
US10/476,968 US6911863B2 (en) | 2001-05-11 | 2002-05-08 | Integrated DVB filter |
EP02727871A EP1393442A1 (en) | 2001-05-11 | 2002-05-08 | Integrated dvb filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10122831A DE10122831A1 (en) | 2001-05-11 | 2001-05-11 | Integrated automatically controlled DVB filter consists of Chebyshev filter with frequency synthesizer to generate control signal |
DE10122831.7 | 2001-05-11 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2002093742A1 true WO2002093742A1 (en) | 2002-11-21 |
Family
ID=7684357
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2002/001614 WO2002093742A1 (en) | 2001-05-11 | 2002-05-08 | Integrated dvb filter |
Country Status (5)
Country | Link |
---|---|
US (1) | US6911863B2 (en) |
EP (1) | EP1393442A1 (en) |
JP (2) | JP2004534444A (en) |
DE (1) | DE10122831A1 (en) |
WO (1) | WO2002093742A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005223439A (en) * | 2004-02-03 | 2005-08-18 | Nec Electronics Corp | Frequency setting circuit |
JP4594375B2 (en) * | 2005-02-09 | 2010-12-08 | アストリウム・リミテッド | Improvement measures for channel filtering in wireless communication systems |
US7583948B2 (en) * | 2005-04-28 | 2009-09-01 | Kabushiki Kaisha Toshiba | Time constant automatic adjusting circuit, filter circuit system, and method of automatically adjusting time constant |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5694439A (en) | 1995-03-21 | 1997-12-02 | Intel Corporation | Bi-directional low pass filtering method and apparatus |
EP0863615A1 (en) | 1997-03-07 | 1998-09-09 | Mitel Semiconductor Limited (Formerly Plessey Semiconductors Limited) | Frequency tracking arrangements |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3688312D1 (en) * | 1985-10-23 | 1993-05-27 | Siemens Ag Albis | EXPANDER SYSTEM FOR PULSE SIGNALS. |
JPH0787332B2 (en) * | 1986-07-18 | 1995-09-20 | 株式会社東芝 | Automatic time constant adjustment circuit for filter circuit |
US5351091A (en) * | 1992-01-14 | 1994-09-27 | Sanyo Electric Co., Ltd. | Burst phase correcting circuit |
JP2707911B2 (en) * | 1992-03-03 | 1998-02-04 | ヤマハ株式会社 | Music synthesizer |
KR100312623B1 (en) * | 1993-02-26 | 2001-12-28 | 이데이 노부유끼 | Active filter circuit device |
JP3208975B2 (en) * | 1993-12-28 | 2001-09-17 | 株式会社日立製作所 | Active filter control method |
US5864442A (en) * | 1995-05-29 | 1999-01-26 | Canon Kabushiki Kaisha | Reproducing apparatus capable of controlling equalization characteristics |
JPH1188789A (en) * | 1997-09-03 | 1999-03-30 | Hitachi Ltd | Receiver for digital broadcast and transmitter for related information |
-
2001
- 2001-05-11 DE DE10122831A patent/DE10122831A1/en not_active Withdrawn
-
2002
- 2002-05-08 JP JP2002590502A patent/JP2004534444A/en active Pending
- 2002-05-08 WO PCT/IB2002/001614 patent/WO2002093742A1/en active Application Filing
- 2002-05-08 EP EP02727871A patent/EP1393442A1/en not_active Withdrawn
- 2002-05-08 US US10/476,968 patent/US6911863B2/en not_active Expired - Fee Related
-
2008
- 2008-05-19 JP JP2008131161A patent/JP2008219942A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5694439A (en) | 1995-03-21 | 1997-12-02 | Intel Corporation | Bi-directional low pass filtering method and apparatus |
EP0863615A1 (en) | 1997-03-07 | 1998-09-09 | Mitel Semiconductor Limited (Formerly Plessey Semiconductors Limited) | Frequency tracking arrangements |
Also Published As
Publication number | Publication date |
---|---|
US6911863B2 (en) | 2005-06-28 |
EP1393442A1 (en) | 2004-03-03 |
JP2008219942A (en) | 2008-09-18 |
US20040145682A1 (en) | 2004-07-29 |
JP2004534444A (en) | 2004-11-11 |
DE10122831A1 (en) | 2002-11-14 |
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